Left 4 Dead 2

Left 4 Dead 2 Crashes with sound loop (ctrl+alt+del lets me go back to the desktop).

OK so my L4D2 is crashing, I have tried every single fix there is out there, disabled the steam overlay, run with -nosound, run on -dxlevel80 -medium, increased paging file size, changed the pagespoolsize in the registry, disabled multicore support, run a clean boot, run windowed, deleted the client.dll and redownloaded it, pretty much every.

I'm at a ♥♥♥♥ing loss, this shouldn't be happening, also not only does this effect L4D2, it effects every source game, I can play for about 15mins or so and then d-d-d-d-d-d etc. Now I'm playing this on a laptop but it's a brand new laptop with nvidia GTX 670M graphics (alongside Intel HD 4000 with optimus), intel i7-3610 processor, 8GB ram. It can play Deus Ex: Human Revolution, Fallout 3 etc. on full specs without any sort of problem. WTF is the problem with source games? I've been waiting to play me some L4D2 for ages as well as Portal 2 and it's making these games impossible to play. There must be some solution out there!

OK. Progress. Tried verifying local cache and it found one file (specifically client.dll) was missing (or more correctly corrupted I guess) suggesting that it's a problem with the source engine itself rather than local hardware etc. letting steam redownload this allowed me a play through of Dead Centre offline (although that was only for 1/2 an hour and afterwards when I got it to verify the cache again sure enough it decided it needed to redownload client.dll again). This also happened in CS:GO which kept crashing. It would be nice if someone from valve could have a look into this as I'm pretty sure I'm not the only one facing this problem.

I'm now reinstalling both L4D2 and CS:GO but I don't have much faith in this solving the problem (as it seems it hasn't really helped other people suffering the same issue).

OK, had a look and I think I've discovered the problem (which fits with games working fine without an internet connection): It's CEG crashing the game on purpose (http://forums.steampowered.com/forums/showthread.php?t=1860006&page=2). FFS I've bought these ♥♥♥♥ing games and I expect to be able to play them without them being crashed ON PURPOSE by trigger happy DRM. Valve, can you ♥♥♥♥ing sort it out?